How can I prevent rendering of objects beneath the floor plane in Unity

I'm building a Unity AR Foundation project, and need my objects to appear from below the floor level. I need to place a floor plane that will render shadows, but more importantly not render the surface material, and should prevent objects beneath it from rendering at all.

I have played with some Depth Mask Shaders but none of them have worked, and are just rendering as a big black hole.

Has anyone achieved this? It must be a common thing for Augmented Reality projects.